Add image extraction functionality with background removal

- Implemented ExtractImageRegion operator for extracting image regions using box or lasso selection.
- Added RemoveImageRegionBackground job for background removal from selected image regions.
- Created utility functions for polygon bounds, selection canvas creation, and applying selection masks.
- Integrated image processing using PIL and numpy for efficient pixel manipulation.
- Enhanced user experience with modal drawing and status updates during extraction.

docs/development.md

@@ -37,7 +37,7 @@ Mesh Plane、Depth Plane、Surface、Background 和 Balloon 按功能组织。
 
 Server 的模型模块返回 Prediction，几何模块处理数组与网格，输出模块写文件。Blender 数据只在 Operator Response 的主线程阶段创建。
 
-Image Lasso 的基础像素裁切在 Blender 主线程完成；启用 Contour 时，Server Job 计算 BEN2 Alpha，并按最终非零 Alpha 范围与像素 Padding 输出图片，Operator Response 负责 Pack 新图、可选复制源 Empty 并更新结果对象的空间范围。
+Image Box、Lasso 与 Perspective 位于 `operators/image_extract/` 功能包。模块职责、交互状态、像素管线、背景清理和 Empty 定位见 [Image 工具技术实现](image-tools-technical.md)。
 
 ## 项目结构